1. Field of the Invention
This invention relates to on-site loose fill packaging and, more particularly, to an apparatus for controllably delivering discrete loose fill particles from a supply to a packaging site and for applying an additive to the loose fill particles to cause the loose fill particles to adhere to each other.
2. Background of the Invention
Packaging of articles for safe shipping and handling is a critical part of virtually all businesses that deal in fragile goods. Those in the packaging industry strive to achieve two, oft times competing, objectives--that of producing low cost packaging that is effective in minimizing breakage/damage of product. Packaging costs become highly critical for goods with low profit margin. As a result, over the years, the packaging industry has become increasingly competitive.
There are presently three primary methods of packaging fragile items--"foam in place", "loose fill", and custom fabricated foam shape packaging. The foam in place technique employs two reactive chemicals which are measured and interacted to instantly produce a low density packaging foam. The foam is directed into article-carrying containers on-site and expands within the constraints of a container to surround, and thereby provide a cushion for, articles within the container.
There are many drawbacks with this packaging technique. The chemical reactants are hazardous. Care must be exercised to protect the system operators. Proper ventilation is recommended in plants and often requires modification to existing systems. Because the polymerization is taking place on-site, the reaction gases, even when vented, tend to pollute the plant environment. Discharge of waste chemical components, and containers therefor, must also be contended with. Further, foam in place packaging cannot be practiced with articles that are heat sensitive because the reaction of components is exothermic. A further drawback with foam in place systems is that the environment therearound is very difficult to keep clean. A still further problem with foam in place systems is that the equipment for processing the same is relatively complicated and requires periodic maintenance. Poorly maintained metering and mixing equipment may produce improper component ratios which minimizes yield and compromises the integrity of the foam end product.
While the foam in place industry has thriven, the above problems have been contended with. The adhesive coated loose fill packaging technique obviates many of the above problems and is, in many applications, a preferred alternative to foam in place.
To produce loose fill, resin material is expanded in bulk by converters worldwide. The resulting expanded particles, referred to commonly in the industry as "peanuts", are shipped in bulk from the converters to individual customers.
Loose fill packaging operations typically gravity feed the discrete, expanded, polystyrene particles into a container for an article to be shipped. At customers' facilities, the peanuts are stored in bulk supply hoppers and normally fed through a depending, flexible conduit which is controlled by the operator to direct a desired amount of the loose fill into a container in which an article is to be shipped. It is known in the art to discharge loose fill into the bottom of an empty container, place an article to be shipped thereover and then cover the article with a further supply of the loose fill.
Product migration within the loose fill is a problem. This is caused by vibrational settling of the product in the carton due to the continued package vibration encountered in the shipping environment. Also, damage caused by abrupt movement or impact to the package is costly to the shipper.
To improve the loose fill cushioning potential and to prevent this migration, The Dow Chemical Company devised a method of coating the particles with an additive/adhesive that bonds the particles to each other to effectively produce, once the additive cures, a solid cushioning block of loose fill particles. The packaging method and additive/adhesive invented by The Dow Chemical Company are described fully in U.S. Pat. Nos. 4,588,638 and 4,644,733, both issued in the name of Dolinar, and assigned to The Dow Chemical Company.
The Dow Chemical Company also has a loose fill dispensing control valve and additive applicator system which it currently markets under its trademark PELASPAN MOLD-A-PAC.TM.. The Dow Chemical Company has been the leader in the loose fill industry and its equipment is considered to be representative of the state of the art. The following is a brief description of The Dow Chemical Company's equipment that is currently being used in the industry.
Heretofore, it was believed important to substantially completely coat virtually all of the individual loose fill particles with additive/adhesive to produce an effective package for fragile goods. To accomplish this, a plurality of nozzles are arranged around the periphery of the loose fill discharge conduit and direct pressurized additive/adhesive towards the center of the conduit. The mixing spray patterns develop a tumbling action on the particles in the adhesive/additive shower, which results in a fairly thorough coverage. Individual solenoid valves are associated with each nozzle and are operated through a central, electromechanical controller which also dictates the opening and closing of a valve to coordinate loose fill discharge with the nozzle operation.
The above system has several drawbacks. First, an excessive amount of adhesive is intentionally delivered through the nozzles to assure that the particle coverage is complete. A pressurized supply of the additive/adhesive impinges on the inside conduit wall at a location that is sufficiently above the bottom of the conduit that the particles can be repeatedly tumbled before falling out of the conduit.
Excess additive/adhesive that drips down the conduit must be collected and dryed by a separate dryer system for subsequent disposal. Over time there is a progressive buildup of the adhesive on the inside surface of the conduit. This buildup occurs sufficiently high above the bottom of the conduit that gaining access thereto is difficult. At a minimum, daily flushing is required. This produces a large quantity of flushed adhesive waste. Disassembly of the entire structure for purposes of cleaning may also be necessitated even with regular flushing.
A further problem with the above system is that there is sufficient thickness of the additive/adhesive on the particles that it takes a considerable length of time to cure. The completed packages must remain in a relatively stationary state until the additive/adhesive cures. The problem of monitoring curing time and storing the packages to be cured is obvious.
A further drawback with the above system is that the electromechanical control unit is relatively complicated and resultingly relatively expensive to manufacture, install and maintain/repair. The latter two operations may require a skilled technician. Further, complicated electromechanical controls are inherently more prone to failure than are their simpler mechanical counterparts. Because additive delivery, flushing and loose fill delivery are all coordinated through the electromechanical control, failure of any part of the control may disable the whole system and result in lengthy system down time.
Because of the large amount of additive that is applied to the loose fill particles, the collected overfill of treated particles is subjected to heat from a 220 volt device to speed up the drying of the additive/adhesive so that the coated particles can be recycled in a reasonably short time. This contributes further to the complication and cost of the system.
A further drawback with the above system is that the intricate flow network for the additive delivery requires a relatively lengthy flushing period.